High speed ring/bus

ABSTRACT

A data communication bus and method of operation thereof, including a plurality of nodes connected to a respective plurality of media segments. A typical node includes an output port coupled to a media segment that it exclusively controls. And an input port coupled to a media segment that is exclusively controlled by another node of the bus. Each media segment typically includes a plurality of high speed data channels such as electrical transmission lines.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 10/190,554,filed Jul. 9, 2002 now U.S. Pat. No. 7,280,549, which claims the benefitof U.S. Provisional Patent Application No. 60/303,719, filed Jul. 9,2001, the disclosures of which are herewith incorporated in theirentireties.

FIELD OF THE INVENTION

The present invention relates generally to data communications systems,and particularly to a high speed data bus architecture.

BACKGROUND OF THE INVENTION

Modern digital and communications and processing systems rely on therapid communication of digital data between components and subsystems.This communication of digital data has been effected using a widevariety of data bus architectures. Typically, wide parallel busarchitectures have been used for short-distance communications ofhigh-speed data, as in digital processors and system backplanes. Wheredata is to be communicated over longer distances, serial data busarchitectures, such as Ethernet, have proven effective. Busses operatingunder the control of a master controller are known in the art, as arepeer-to-peer networks. There is, however, an opportunity to improve theperformance of many systems by the introduction of a superior high-speeddata bus architecture.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a high-speed data bus made up of aplurality of local nodes coupled to one another by high speed mediasegments. Typically the nodes and media segments are configured in aring structure. Data bearing messages are passed sequentially from nodeto node along intervening media segments. In one aspect, each mediasegment is composed of a plurality of parallel transmission line(T-line) channels. In another aspect, data signals are transmitted inserial fashion on the parallel-configured T-line channels, such thatsignal transit time over a particular media segment is longer than theminimum time between bit transitions. In a further aspect of theinvention, incoming and outgoing data is buffered at each node so that amessage being received by a node may differ from a messagesimultaneously being transmitted by the same node. In another aspect, anode according to the invention includes a data synchronizer adapted toperform phase alignment and bit alignment on data signals in parallelT-line channels. In a further aspect, the invention includes ahigh-speed clock signal used by the data synchronizer to align signals.The high-speed clock signal may be encoded in the transmitted data andextracted therefrom, or may be transmitted on a separate high speedclock signal line. In yet another aspect of the invention each node of aring/bus is a bus master node with respect to the transmission of dataon a media segment coupled to an output of the node. The same node is aslave with respect to the reception of data on a media segment coupledto an input of the node.

The above and other features and advantages of the invention will bemore readily understood from the following detailed description of theinvention which is provided in connection with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a high speed bus according to one aspect of the invention;

FIG. 2 shows an exemplary data packet structure for transmission on thehigh speed bus;

FIG. 3 shows a portion of an exemplary media segment showing threestrip-line transmission lines;

FIG. 4 shows a portion of an exemplary bus node in block-diagram formaccording to one aspect of the invention;

FIG. 5 shows an exemplary data synchronizer circuit in block diagramform according to one aspect of the invention;

FIGS. 6A-F show data signal timing relationships according to one aspectof the invention;

FIG. 7A shows a flow chart summarizing a portion of the operation of anexemplary node according to one aspect of the invention;

FIG. 7B shows a flow chart summarizing a portion of the operation of anexemplary node according to one aspect of the invention;

FIG. 8A shows an exemplary embodiment of a communication networkaccording to the invention;

FIG. 8B shows an exemplary embodiment of a communication networkaccording to the invention;

FIG. 9 shows a computer system including a memory prepared according tothe invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those of ordinary skill in the art to make and use the invention,and it is to be understood that structural, logical or proceduralchanges may be made to the specific embodiments disclosed withoutdeparting from the spirit and scope of the present invention.

FIG. 1 depicts a simplified block diagram of a high speed data bussystem 100, in accordance with an exemplary embodiment of the invention.As shown, four nodes, A, B, C and D are coupled together by fourrespective media segments 102, 104, 106 and 108. In one aspect of theinvention, each of the four nodes embodies similar structure, andprovides correspondingly similar function. The nodes operate in apeer-to-peer relationship to one another inasmuch as no one node is amaster to the entire bus. Data moves from node to node across the mediasegments in a single (here clockwise) direction. A wide variety ofconventions may be employed with respect to data transmission. In theillustrated embodiments, the data is transmitted in discrete packets.Exemplary packets are shown being transmitted in FIG. 1. For example,packet 110 is shown being transmitted from node A to node B, packet 112is shown being transmitted from node B to node C; packet 114 is shownbeing transmitted from node C to node D; and packet 116 is shown beingtransmitted from node D to node A. It should be noted that, according toone aspect of the invention, packets 110, 112, 114 and 116 representcompletely different messages transmitted simultaneously over differentmedia segments of the data bus.

FIG. 2 depicts an exemplary packet structure 200 used in the high speeddata bus system 100 of FIG. 1. The exemplary packet structure shown isadapted for use in a distributed Content Accessible Memory (CAM) system,as described in copending patent application Ser. No. 10/179,383. Forpurposes of simplicity, the packet structure 200 is depicted ascontaining five fields. A first field is a source node (or origin) field205. The source node field 205 identifies the CAM from which the commandwas originally issued and to which CAM the result must be returned.

A second field of the packet structure 200 is the request identificationfield 210. The request identification field 210 contains theidentification for a particular command originated at a local node. Therequest identification field 210 is used to associate a command with aresponse received from one of the CAMs. The response contains the samerequest identification as the original command. Alternatively, therequest identification can be viewed as an identification number of thepacket.

The third field of the packet structure 200 is a command field 215. Thecommand contained therein is selected from a command set pre-defined foruse in a particular application.

The fourth field of the packet structure 200 is the data length field220. The data length field 220 indicates the number of data bytes in thepacket. The data 225 itself is also included in the packet structure 200as the fifth field. Generally, the amount of data contained in thepacket structure 200 is command and implementation dependent.

FIG. 3 shows a portion of an exemplary media segment, according to oneaspect of the invention. The media segment 280 includes three strip-lineT-lines, of a form known in the art. Each transmission line includesrespective first 282 and second 284 conductors disposed in substantiallyparallel spaced relation to one another on respective opposite sides ofa respective dielectric region 286. The embodiment shown includes twoT-lines allocated to the transmission of data (bit-0 288 and bit-1 290)and a third T-line 292 allocated to carry a high speed clock signal. Asis discussed in further detail below, the presence of the separate clockline 292 is optional, as is the number of data transmission T-linesAlthough the embodiment shown includes strip line conductors, othermedia such as coaxial cable, microwave wave-guides, optical fibers,coherent free-space transmission, or other media formats known in theart, may be used alone or in combination.

FIG. 4 shows an exemplary node 150 of a high speed data bus system, inblock diagram form. One preferred embodiment of the invention is shown,in which the data path of the high speed media is 2 bits wide (bit 0,bit 1). In other preferred embodiments, the data path is 8, 16 or 32bits wide. Other data widths may be routinely selected, depending on thetechnical demands of a particular application.

The node 150 includes an input port 302 and an output port 304. Theinput port includes a first differential amplifier input 306 of a firstinput amplifier 308 and a second differential input 310 of a secondinput amplifier 312. Also, included in the FIG. 4 embodiment is a thirddifferential input 314 of a third input amplifier 316, where the thirddifferential input is adapted to receive a high speed clock signal.Following the bit-0 data path through the node, one sees that the inputamplifier 308 is coupled at a differential output to a first input 320of a data synchronizer circuit 322. In the embodiment shown, thiscoupling is made by means of a differential signal line 324. The datasynchronizer circuit 322 includes a signal input 325 coupled to a clockoutput 327 of a clock divider and synchronization control circuit 329for receiving a first clock signal. However, single endedinterconnections may be used instead of the differential, everywhere inthe node.

The data synchronizer circuit 322 is coupled at an output 326 to aninput of a deserializer circuit 328. An output of the deserializercircuit is coupled to a first input 330 of an input FIFO buffer circuit332. The input FIFO buffer circuit 332 includes a further input 334adapted to receive a second clock signal, and an output 336 coupled to afirst input 338 of a formatter, interface and control (FIC) circuit 340.

The deserializer 328 is a demultiplexer that receives a single bit-wideinput from line 342 and outputs a multi-bit-wide output on line 344.Thus, for example, if line 344 is 8-bits wide, 8 bits received in serialfashion at the input of the deserializer are output in parallel as asingle 8-bit wide word at the output of the deserializer 328.

In this exemplary case, the input FIFO buffer 332 is 8-bits wide,corresponding to the width of the deserializer 328 output.

As is readily understood, the rate at which data is clocked out of thedeserializer is slower than the rate at which it is clocked in by afactor equal to the ratio of output data width to input data width.

In the exemplary embodiment of FIG. 4, the coupling 342 between the datasynchronizer circuit 322 and the deserializer circuit 328 is asingle-ended signal line. So too, the coupling 344 between thedeserializer and the FIFO input buffer and the coupling 346 between theFIFO input buffer and the FIC circuit 340 both include single-endedsignal lines. Also, the second clock signal is shown to be conveyedwithin the node 150 on a single-ended signal line 348. One of skill inthe art would routinely select single-ended and differential couplinglines for use within the system according to the demands of a particularapplication.

A first output 352 of FIC circuit 340 is coupled by a single-endedsignal line 354 to a first input 356 of an output FIFO buffer 358. Athird clock signal is coupled from a second output 360 of the FICcircuit 340 to a second (clock) input 362 of output FIFO buffer 358 by asingle-ended signal line 364. An output of the output FIFO buffer 358 iscoupled through a further single-ended signal line 366 to an input of aserializer circuit 368. The serializer circuit includes a differentialoutput 370 coupled through a differential signal line 372 to adifferential input of an output amplifier 374. An output of the outputamplifier 374 forms a portion of output port 304, and is coupled to afurther T-line 288 of a further media segment.

The bit-1 signal path includes a respective input amplifier 312, datasynchronizer circuit 390, deserializer circuit 392, FIFO input buffer394, FIFO output buffer 396, serializer circuit 398, and outputamplifier 400, coupled to one another, and to the FIC circuit 340 in thesame manner, and operating the same way, as the corresponding componentsof the bit-0 signal path.

As discussed above, a high speed clock signal is transmitted from nodeto node around the ring on a high-speed clock signal line 401. Inanother embodiment of the invention, the high speed clock signal isencoded into the data transmitted from node to node, so that no separatehigh speed clock signal line is needed. In one aspect of the inventionany node on the ring may be arbitrarily selected to originate the clocksignal for the ring. In another aspect of the invention, responsibilityfor clock generation may be passed from node to node depending, forexample, on a timed interval. Alternately, the clock signal mayoriginate from a clock circuit that is separate from any node. Also,every node may generate and output its own clock to be used in the ringsegment over which the node is the master.

The FIC circuit also includes a data input 404 for receiving input datafrom the bit-1 data path, a control output 339 for controlling data flowout of the input FIFO buffer, and a data output 406 for outputting datato the bit-1 data path. A clock output 408 outputs a fourth clocksignal, generated by the FIC, over a clock line 410 to a clock input 412of an application circuit 414. In FIG. 4, “P”, “Q” and “R” representdata path widths being routinely implemented according to therequirements of a particular application. A control input/output 416outputs control signals over a P-bit wide control bus 418 data path to acontrol input/output 420 of the application circuit 414. An addressinput/output 422 outputs address signals over a Q-bit wide address bus424 data path to an address input/output 426 of the application circuit414, and a data input/output 428 of the FIC outputs data signals over anR-bit wide data bus 430 data path to a data input/output 432 of theapplication circuit 414.

FIG. 5 shows an exemplary data synchronizer circuit as in FIG. 4, inadditional detail. The data synchronizer circuit (eg. 322) includes aphase alignment circuit 450, and a bit alignment circuit 452. A clocksignal received at input 325 of the data synchronizer is coupled by aclock line 454 to a clock input 456 of the phase alignment circuit and afurther clock input 458 of the bit alignment circuit.

The phase alignment circuit 450 includes an adjustable delay line 460and a delay control circuit 462 bidirectionally coupled to the delayline at 464. In an alternate embodiment, a multi-tap delay line is usedin place of the adjustable delay line 460. The bit-alignment circuitincludes a shift register 466 and a bit control circuit 468bidirectionally coupled to the shift register at 470.

Together, the phase alignment circuit and the bit-alignment circuit actto correct for unequal signal transmission delays exhibited by signalsconveyed by, for example, the bit-0 288 and bit-1 290 T-lines. As shownin FIG. 6A, a first signal 700 including a first signal transition 702is transmitted on the bit-0 T-line 288. A second signal 704 including asecond signal transition 706 is transmitted on the bit-1 T-line 290. Atthe input to a particular media segment, both the bit-0 transition andthe bit-1 transition occur simultaneously at time t_(o). Due todifferences in the length and/or electrical characteristics of the bit-0288 and bit-1 290 T-lines, the two transitions are no longersynchronized when they reach the output end of the media segment. Thisis shown in FIG. 6B where signal transition 702 arrives at a receivingnode at time t_(a) prior to the arrival of transition 706 at time t_(a).In practice, such de-synchronization of signal transitions can causedata errors. Accordingly, it is the function of the phase alignmentcircuit to re-align the two signal transitions so as to insure dataintegrity.

In FIG. 6C, the two signal transitions are shown realigned at timet_(b), after having passed through the phase alignment circuit. Inoperation, a calibration cycle is executed during which respective bit-0and bit-1 signal transitions known to be simultaneously issued aredetected. Any media-induced delay is ascertained, and used to set adelay factor imposed by the delay line 460 that is applied to the buschannel with the smallest intrinsic delay (and thus the first-arrivingsignal). This delay factor remains in effect after the calibration cycleis complete, and acts to delay what would otherwise be early-arrivingsignal transitions so that a later-arriving signal has a chance to catchup. As would be understood in the art, calibration of the delay line mayoccur once or repeatedly, according to the stability of the transmissionmedia and the requirements of the particular application.

The bit-alignment circuit performs a function similar to that of thephase-alignment circuit, but at a bit/word level. Depending on thecharacteristics of the respective T-lines and the frequency of datatransmission, the phase differential introduced during transmission overa particular media segment may exceed one bit-time. This effect is shownin the bit-0 line and bit-1 line signals shown in FIG. 6D whichillustrates two signals (bit-0 712, bit-1 714) with respective firsttransitions 716, 718 transmitted at time t_(o). In such a case, as shownin FIG. 6E, simple alignment of signal phase may not properly align thesignals as transmitted. In FIG. 6E, one sees that excessive delay in theT-line bearing signal 714 causes transition 718 to arrive at a receivingnode at time t_(c)′, well after transition 716 which arrives at the samenode at time t_(c). Consequently, after phase alignment (as describedabove) transition 718 aligns, incorrectly, with transition 720, ratherthan transition 716. The evident consequence is a loss of dataintegrity. Therefore, it is necessary to phase-shift incoming datasignals sufficiently so as to insure that corresponding data bits of thebit-0 and bit-1 lines are processed simultaneously. This is achieved byshifting the phase-aligned signals from each T-line into respectiveshift registers, and tapping signals out of the respective shiftregister at respective points that eliminate the undesirablemisalignment shown in FIG. 6E. FIG. 6F shows the shifted result withdata signals both phase-aligned and bit-aligned at time t_(d).

The operation of the FIG. 1 embodiment of the high speed ring/busincluding nodes of the FIG. 4 embodiment will now be described inadditional detail.

In general operation, an application circuit 414 of node A generates amessage to be sent, for example to a corresponding application circuit414 of node D. The data comprising the message to be sent is packaged ina packet structure including a header having origin and destinationinformation along with information characterizing the payload of data(for example data length may be included, along with a CRC value that isused to confirm data integrity). The packet is transmitted over thewide, low-speed data bus 430 in words of width R from the applicationcircuit to the FIC circuit 340 of node A. In the FIC circuit,inter-packet data may be added, such as error checking/correcting codesor other data further characterizing the complete packet, or supportingring operation. Inter-packet data includes data that is added to thedata stream passing around the high speed bus that is not part of thepayload and headers of a regular packet. This data may be appended bythe FIC circuit to a data packet prepared by an application circuit.Alternately, it may be a special packet originating with the FIC, andhaving a format that is like that of a regular packet, or completelydifferent. In one aspect of the invention, repeated packet origin anddestination information is included in this inter-packet data. Thepackaged data that was received (and optionally processed) by the FICcircuit in words of R bits wide is broken into words N-bits wide whereN<R. These N-bit wide words are each allocated to one of a plurality ofoutgoing bitstreams. In the FIG. 4 embodiment, 2 bit streams areavailable (bit-1, bit-0). Accordingly, in a typical applicationaccording to FIG. 4, the relationship between the widths of lines 430(R) and 354 (N) would be R=2×N. Proceeding along the bit-0 data path,data is then transferred in N-bit wide words over line 354 to the outputFIFO buffer 358 which stores the data it receives as words of width N.

A clock signal is provided by the FIC circuit at its clock output 360,to the output FIFO buffer 358. Under the control of this clock signal,the output FIFO buffer 358 transfers data in N-bit words to theserializer 368. The serializer receives the data in N-bit wide words ata given clock rate and outputs the data at a clock rate N-times fasterin a one-bit wide stream. Concurrently, along the bit-1 data path, datais passed out of the FIC circuit 340 in N-bit wide words, buffered inFIFO 396, and serialized into a one-bit wide output signal by serializer398.

Output amplifiers 374 and 400 each amplify respective one-bit wide datasignals and send the signals out over their respective T-lines (288,290) of a media segment 102 coupled to node A 150 at output port 304.These bit-0 and bit-1 data signals are then received at input port 302of node B. Specifically the bit-0 data stream is received at input 306of amplifier 308 and the bit-1 data stream is received at input 310 ofamplifier 312. The input amplifiers 308, 312 are designed in routinefashion to have an input impedance matched to the impedance of therespective T-line (288, 290) to which each is respectively coupled. Thisserves to minimize signal reflection. Also, in the illustratedembodiment, the respective amplifier inputs 306, 310 are implemented asdifferential inputs, preferably with a high common node rejection ratio(CMRR).

The bit-0 input amplifier 308 supplies an amplified copy of the datasignal it receives to the bit-0 data synchronizer 322. Concurrently, thebit-1 input amplifier supplies an amplified bit-1 data signal to thebit-1 data synchronizer 390.

At the same time a clock signal is supplied to the two datasynchronizers at their respective clock inputs 325, 326 by the clockdivider and synchronization control circuit 329.

As described above in relation to FIG. 5, the data synchronizers 322,390 perform a phase alignment and a bit alignment on the two datasignals. Consequently, at the respective inputs of the respectivedeserializers 328 and 392, the bit-0 and bit-1 data streams are properlyaligned. The two deserializers 328, 392 concurrently demultiplex the twoincoming data signals from single bit wide signals into respective N-bitwide data streams.

The N-bit wide data streams are slowed by demultiplexing to a clock rate1/N times as fast as the clock speed of the data found on the incomingT-line (at port 302). N-bit wide data is passed concurrently fromdeserializers 328, 392 to input FIFO buffers 332, 394 according to theclock signal provided on clock line 348. Each FIFO buffer, in turn,passes N-bit wide data to the FIC circuit 340 at inputs 338 and 404 forthe bit-0 and bit-1 data streams respectively.

The FIC circuit 340 evaluates the incoming data to see whether it isdestined for the instant node (here node B). If so, the data is passedto the local application circuit 414. If not, the data is passed throughto the respective FIC outputs 352, 406 of the FIC circuit. In oneembodiment of the invention, the determination of data destination ismade by evaluating inter-packet data. In another embodiment of theinvention, destination information from within the packet is evaluatedto ascertain packet destination.

In the present example, the data being transmitted is destined for nodeD rather than node B, therefore the FIC circuit 340 will pass the datafrom its inputs 338, 404 to respective outputs 352, 406. However, ifupon the arrival of the incoming data at inputs 338, 404, the FIC 340 isalready sending data (for example, data that originated with the node Bapplication circuit 414) then, in one aspect of the invention, theincoming data is buffered in the incoming FIFO buffers 332, 394 untiltransmission of the outgoing data (for a destined portion thereof, e.g.,packet) is complete. Note that a portion of the incoming data stream maybe buffered in additional registers coupled to FIC inputs 338, 404within the FIC 340. Data stored within these additional registers may beevaluated for control purposes.

It should be noted that, in one aspect of the invention, a priorityscheme is established such that incoming data may be prioritized overoutgoing data. This prioritization may be controlled by a conventionthat always gives priority to incoming data, or alternately, by acomparison within the FIC circuit 340 of priority designation of datacontained within the two incoming data streams. Note that the prioritydata may be contained within a packet, or may be transferred asinter-packet data that is generated by the FIC or the applicationcircuit, depending on the particular application, and may be inserted ina data stream under hardware or software control.

The data output by node B on media segment 104 is received by node C,which performs the same functions detailed above with respect to node B.Again, the data is not destined for node C, and so it is passed throughnode C and transmitted over media segment 106 to node D. At node D, theinput data is received, amplified, synchronized, deserialized, bufferedand transferred to the FIC circuit 340. In the FIC circuit, thedestination portion of the data stream is examined to ascertain that thecurrent node is the destination node. The N-bit wide data words of thebit-0 data stream are then combined (typically concatenated) with theN-bit wide words of the bit-1 data stream to form, for example, R-bitwide data words that are passed over the local data line 430 to the nodeD application circuit 414.

The flowchart of FIG. 7 summarizes a portion of the operation of a nodewith respect to signals received at input port 302, and shows the dataprocessing portion 516 that takes place within the FIC circuit 340, asdiscussed above. The overall data stream routing process 500 includesreceiving data 502 at a node. The data signal is received at a devicewith an input impedance matched to the media segment to which it iscoupled for receiving. The data signal is then amplified 504 in an inputamplifier that may have positive, negative, or unity gain as required bya particular application.

In a next step, plural data signals received on respective data pathsare synchronized 506. This data synchronization includes phase alignment508 and bit alignment 510, as previously described. Thereafter, the datasignals are deserialized 512 by demultiplexing. This widens andcorrespondingly slows the data stream. The words of the wide data streamthat results are stored 514 in a FIFO buffer. This allows the receipt ofan incoming data stream while the FIC is otherwise occupied, e.g., withtransmission of outgoing data originating at the present node. Afterstorage in the FIFO buffer, data is evaluated and processed in the FICat process segment 516. FIC processing includes evaluation of datadestination information. The data destination is extracted 518 accordingto the format of the data. Typically, it is found in a packet header orin inter-packet data. Once extracted from the data stream, destinationinformation is evaluated 520 to determine whether the present data(e.g., data packet) is destined for the current node. If so, anyrequired pre-processing 522 such as removal of inter-packet data,stripping of packet headers, error checking/correction, and/oraggregation of data into wider parallel format, is performed.Thereafter, in one embodiment, data from the data stream is passed 524over a correspondingly wide and slow data bus to a local userapplication circuit of the node.

As would be understood by one of skill in the art, one node of ahigh-speed bus according to the invention may serve as a gateway to oneor more application circuits standing alone or configured in a widevariety of communication networks. Such communication networks mayinclude further instances and embodiments of a communication system asdescribed herein.

Referring again to FIG. 7A, in one embodiment of the invention, if thedestination extracted 518 from the data stream does not match thecurrent node, the node extracts origin information 526. In a ringstructure embodiment of the invention, one possible failure mode is thatinformation is not recognized by a destination node or is otherwisepassed all the way around the ring to its originating node. Therefore inone aspect, the present node compares the extracted origin informationto its own address 528 to confirm that the data has not inadvertentlybeen passed all the way around the ring network without being acceptedby a receiving node. If data is found to have completely traversed thering, appropriate error handling may be applied 530. In an alternativeembodiment, a data packet is always passed completely around the ring,e.g. to confirm ring integrity, while a copy of the data is left behindat the destination node. It should be noted that selection of theparticular order in which the various information, such as origin anddestination addresses within a data stream, is handled would be a matterof routine design for one of skill in the art. Moreover, the functionspresented herein are merely exemplary of the data processing that wouldbe performed to execute the data routing function of the FIC ascharacterized herein.

In the common case, where data of the data stream neither originated at,nor is destined for, the present node, the data stream is passed out ofthe FIC and stored 532 in the output FIFO buffer. This data stream maybe an exact reproduction of the incoming stream as synchronized (at 506)or it may include network history information added by the FIC relatedto passage through the present node. The information of the data streamis held in the FIFO until it can be serialized 534 (i.e. multiplexed)into a narrower data stream with a correspondingly higher clock rate.The signal of this narrower data stream is then amplified 536 by anamplifier with an output impedance that is matched to the outgoing mediasegment and output 538 onto that media segment for transmission to thenext sequential node.

FIG. 7B shows a flow chart that summarizes the processing 600 of dataoriginating at the application circuit 414 of a particular node. Thedata is received 602 (e.g. at input/output 428) of the FIC circuit.Typically, the data received is already configured in a data packet suchas that described above in relation to FIG. 2. In addition, address andcontrol data may be received 604 at respective input/outputs 422, 416 ofthe FIC circuit.

In one embodiment of the invention, the FIC circuit adds interpacketdata 606 characterizing the packet (e.g. error checking/correction,transmission timestamp, etc.) to the packet data. The combined datapacket and interpacket data form a data stream that is then divided intoplural streams 608 according to the number of data bit streams of themedia segment (two streams for the FIG. 4 embodiment). Next, the data istransferred 532 to the output FIFO buffer in N bit wide words.Thereafter, the data is serialized 534 in to one-bit wide data streamswhich are amplified 536 and output 538 onto the media segment connectedat output port 304.

At this point, one should recognize that each node (A, B, C, D) controlsthe media segment (102, 104, 106, 108) connected at its respectiveoutput port 304. In one aspect, port 304 is unidirectional (outgoing)and only that node may send data on the media segment. Accordingly,there is no exchange of a control token, and no opportunity for signalsto collide on the data bus. The inefficiencies of token ring andcollision-based systems are thus avoided.

The system is a peer-to-peer system in the sense that each node isstructurally and functionally similar to every other node of the ring.Each is the master of the media segment coupled at its output port 304and the slave (with respect to receiving data) of the media segment atits input port 302.

As is readily understood, the ring bus structure illustrated in FIG. 1is only one of a wide variety of configurations that are routinelyderived from the foregoing disclosure according to the requirements of aparticular application. In other aspects, as shown in FIG. 8A, theinvention includes a network 550 with plural counter directional ringsincluding nodes 552 and media segments 554. Alternately, (for example),multiple linked rings may be configured as shown in FIG. 8B. A ringstructure is not, however, required and linear or other configurationsmay be employed where unidirectional transmission is desired or, where amechanism for reversing the direction of information flow, as necessary,is provided.

With respect to clocking of the system, while in one aspect the nodesoperate as co-equals on a ring, one node may be designated totemporarily or permanently supply a clocking signal for the entire ring.Alternately, generation of the clock signal is a task that may beperiodically assumed by different nodes. It is not, however, essentialthat a single clock signal be utilized by the entire network. Since eachnode controls its outgoing media segment, different clock signals may beemployed on different media segments.

As alluded to above, one application for the high speed bus of thepresent invention is in the aggregation of a plurality of integratedcircuit devices, e.g., memory devices, into a cooperating high speedunit. Thus, for example, multiple CAM devices may be configured tooperate in coordinated fashion by communicating with one anotheraccording to the present invention. The invention is not so limited,however, and may be employed in a wide variety of data processingsystems.

FIG. 9, for example, shows a generalized digital system 900 in whichprocessor, memory, and other components are spatially distributed andconnected to one another by a high speed bus according to one aspect ofthe invention. Accordingly, a central processing unit 902, a memory unit904, a user interface unit 906, a disk storage unit 908, and an I/O unit910 are each coupled to the high speed bus 912 by respective nodes 150.Digital data is passed between the nodes according to a protocolroutinely adapted from the foregoing disclosure to the requirements ofthe particular system illustrated.

According to a further aspect of the invention, the memory unit 904includes a plurality of memory modules 920 (e.g. RAM integrated circuitdevices, CAM integrated circuit devices, etc.) mutually coupled by afurther high speed data bus 922. The memory modules 920 are each coupledto the further bus 922 by a node 150 which may be discrete from thememory device, or which alternately may be integrated with the memorymodule 920, as shown.

While preferred embodiments of the invention have been described in theillustrations above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,deletion, substitution, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as limited by theforegoing description but is only limited by the scope of the appendedclaims.

1. A network comprising: a first node circuit having an input port andan output port, said input port adapted to receive a first data signalfrom a second node circuit across a first media segment coupled betweensaid second and first node circuits, said first media segment beingadapted to be controlled by said second node circuit during a particulartime period, said output port adapted to transmit a second data signalfrom said first node circuit to a third node circuit over a second mediasegment coupled between said first and third node circuits wherein saidsecond media segment is adapted to be controlled by said first nodecircuit during said particular time period, wherein said first nodecircuit further comprises: a data synchronizer for aligning signaltransitions and data words of the first data signal; a deserializer fordemultiplexing said first data signal into first data; an input FIFObuffer for storing said first data; a control circuit for routing dataflows of said first data; an output FIFO buffer for storing an outgoingdata, the control circuit being directly coupled to the input and outputFIFO buffers and providing a clock signal to the output FIFO buffer; anda serializer for multiplexing said outgoing data into said second datasignal.
 2. A network as defined in claim 1, in which said controlcircuit is adapted to direct said first data to either a localapplication circuit, or to said output FIFO buffer.
 3. A network asdefined in claim 2 in which said control circuit is adapted modify adata component of said second data signal.
 4. A network as defined inclaim 1 wherein said data synchronizer is adapted to align network dataand comprises: a phase alignment device adapted to align a signaltransition; and a bit alignment device adapted to align concurrent databits.
 5. A network as defined in claim 1, wherein each media segmentincludes a respective plurality of serial data transmission lines.
 6. Anetwork as defined in claim 1, wherein each node circuit includes asignal routing device adapted to route a data signal received at saidrespective input to either a respective local bus connection of saidrespective node circuit or to said respective output of said respectivenode circuit.
 7. A data communication node adapted to perform a sequenceof data communication steps comprising: receiving a messaging unit froma transmission line; synchronizing said messaging unit; deserializingsaid messaging unit; storing said deserialized messaging unit in abuffer; transferring said deserialized messaging unit to a formatterunit; evaluating said transferred deserialized messaging unit todetermine keep or pass-through data; transferring determined keep datato a local bus; passing determined pass-through data to an outputbuffer; clocking the output buffer from a circuit used to evaluate saidtransferred deserialized messaging unit; serializing determinedpass-through data from said output buffer, and transmitting saidserialized pass-through data to a further data node.
 8. The node ofclaim 7, wherein said synchronizing step comprises phase alignment ofthe message unit.
 9. The node of claim 7, wherein said synchronizingstep comprises bit alignment of the message unit.
 10. The node of claim7 further adapted to perform the step of amplifying the receivedmessaging unit.
 11. The node of claim 7 further adapted to perform thestep of amplifying the serialized data.
 12. The node of claim 7, whereinsaid evaluating step comprises extracting destination data to determinea destination for the messaging unit.
 13. The node of claim 7, whereinsaid transferring step comprises pre-processing the determined keepdata.
 14. The node of claim 7, wherein the passing step comprisesextracting origin data associated with the received messaging unit. 15.The node of claim 7 further adapted to perform the step of errorhandling when the messaging unit contains an error.
 16. A communicationmethod comprising: receiving a messaging unit from a transmission line;synchronizing the messaging unit; deserializing the synchronizedmessaging unit; evaluating the deserialized messaging unit to determinewhether to keep the deserialized messaging unit or pass it through toanother device; if it is determined that the deserialized messaging unitshould be kept, transferring the deserialized messaging unit to a localbus and providing a clock for the transferring step from a circuit usedfor the evaluating step; and if it is determined that the deserializedmessaging unit should be passed through to another device, passing thedeserialized messaging unit to another device and providing a clock forthe passing step from the circuit used for the evaluating step.
 17. Themethod of claim 16 wherein said synchronizing step comprises phasealignment and bit alignment of the message unit.
 18. The method of claim16, wherein said evaluating step comprises extracting destination datato determine a destination for the messaging unit.
 19. The method ofclaim 16, wherein said transferring step comprises pre-processing thedetermined keep data.
 20. The method of claim 16, wherein the passingstep comprises extracting origin data associated with the receivedmessaging unit.
 21. The method of claim 16 further adapted to performthe step of error handling when the messaging unit contains an error.22. The method of claim 16, wherein the passing step comprises: passingdetermined pass-through data to an output buffer; serializing determinedpass-through data from said output buffer, and transmitting saidserialized pass-through data to a further data node.
 23. A node circuitfor a network, said node circuit comprising: a data synchronizer forinputting a first data signal; a deserializer for demultiplexing saidfirst data signal into first data; a control circuit for routing dataflows of said first data; an output FIFO buffer for storing an outgoingdata, said control circuit being directly coupled to the output FIFObuffer and for providing a clock signal to the output FIFO buffer; and aserializer for multiplexing said outgoing data into said second datasignal.